Sen. Ted Cruz’s filibuster had become the fourth-longest in Senate history and was still going Wednesday morning, as the Texas Republican continued to hold the chamber floor to highlight the GOP’s effort to defund Obamacare.

He took control of the floor at 2:41 Tuesday afternoon and crossed the 18-hour, 23-minute mark at 9:04 Wednesday morning, officially passing Sen. Robert La Follette Sr.’s filibuster in 1908.

Mr. Cruz was trying to rally both Republicans and Democrats to defy their leaders and vote to block action on a stopgap spending bill, arguing that it was the only way to force Democratic leaders, who control the chamber, to relent and allow a more robust debate on whether to fund the health care law.